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XR200R Weight Reduction

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Swiss,

Any idea what years/model older ktms had the same diameter triples as the ktm85? Any idea how much more offset they have?

Chuck- newer crf front calipers are a direct swap for front xr stuff. Can save a bit of weight there but not too cost effective. I had to completely modify my late 90's xr250 rear bracket to mount the 2006 crf250r rear brake on my xr600 swingarm, was yours a bolt on deal?

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Good question on the rear calipers. Mine was a bolt on with a XR caliper bracket to suit the 17mm axle and the SA, the caliper is an XR type. I realize when looking at my collection of calipers that my CRF250R rear brake isn't on a bike!! So my XR has a XR rear brake, I corrected my earlier post.

All of the Honda rear calipers that I have and late CRFs fall into two groups; early, and late CRF. The differences are:

pin spacing; early 70mm, late 65mm.

Pads; early rectangular pads, late squarish pads.

banjo fitting; early on bottom, late on front side.

XRs use a slot for the axle, others a hole.

A variety of mounts for the rotor shield.

The XR bracket on my bike has bosses for the rotor shield.

I have an 08 CRF230L rear brake and the bracket looks like the CRF bracket but the axle hole is smaller, and it uses the early caliper with the long pads.

A good cross reference and application guide for brakes is the downloadable EBC catalog. The early calipers use FA131 pads the late FA346.

Edited by chuck4788

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Swiss,

Any idea what years/model older ktms had the same diameter triples as the ktm85? Any idea how much more offset they have?

Chuck- newer crf front calipers are a direct swap for front xr stuff. Can save a bit of weight there but not too cost effective. I had to completely modify my late 90's xr250 rear bracket to mount the 2006 crf250r rear brake on my xr600 swingarm, was yours a bolt on deal?

No, the only other set of KTM forks that I have is an early 4054 USD fork. It uses the same diameter for both the upper and lower clamps. The newer clamps use larger clamps for the lower and smaller for the upper. The KTM 85/105 uses 53mm lower and 49mm upper clamps. It seems from the specs that I have seen the larger bikes come with about 6mm more offset than the mini-bike forks do. Just need to find out what the clamping diameters are for the '90s 43mm forks. And the fork spacing will probably be a bit wider on the big bike forks but I again don't have a set so can't say for sure. Just looked at a set for a KTM 300 and they state uses 50mm tubes and 190mm c-c spacing. The 85 forks have 175mm c-c spacing.

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205 wo the headlite.

Pull the case guards: ............ 1.5 lbs

XR100 tanks, save: .............. 1.025 lbs

pull Scotts steering damper: . 1.4 lbs

Custom foot peg brackets: .....1 lbs (expensive)

switch rear tire to a D756: ..... 2 lbs

pull side stand: ...................... 1.5 lbs

Drill seat base: ..................... 1 lb per

So several ways to get under 200lbs.

Chuck, going back to this old post.  Note that the '83 XR200R tank weighs just over 5lbs. and I am sure that your newer one does also.  Rather than use the much smaller capacity XR100 tank you should consider the Clarke XR200 replacement tank.  It only weighs 3lb. 14oz. and carries 2.7gal. of gas.  That should be at lease 1lb lighter than your XR200 Honda tank.  So swapping the tank, you said you already pulled the Scotts damper, switching the rear tire and drilling the seat base would net you a loss of just over 5lbs. which would put you under your 200lb. goal.  If you left the trials tire on you would be under 202lbs.  IF you used a CRF85/150 rear wheel with the smaller caliper etc. and an 18" rim it would probably put you close to the 200lb. mark again.  Fixing to post some pages and weights to the Lite-Bikes.com website probably tomorrow to work with Doug/Ryder and get things going.  Some of the newer handlebar mounted LED lights would probably also weigh next to nothing and allow you to keep a headlight on the front with the benefit of low current draw of the LEDs.

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Good points. The XR100 tank was nearly as high as the XR200 tank so the only advantage was a smaller fuel load, no significant  improvement in cockpit ergonomics.

I've been absent for the last few weeks because of the need to finish up behind schedule items so we can leave for AZ, once we get south I'll have more time to respond. 

It is easy to say such and such weight is the goal but I feel that is not as important as moving the weights as close to the CG of the bike as possible. So reducing up high weight such as handle bars, or fuel tank, are more important than reducing foot peg weight because the former are further from the CG. This has to do with vertical polar moment of inertia; in the car world horizontal polar moment of inertia is a criteria for agile handling. I feel that the vertical is important for our control of dirt bikes, I guess this is referred to as "flickable". As an example I've placed a 1 lb  foot peg weight reduction low on the list list compared to a 1 lb reduction of handle bar weight by using Renthal bars because of their relative distances from the CG of the bike.

An example are two Montesa Trials bikes owned by a friend and I ; one is a 2T the other a 4t, 10 lbs of weight differences but much different feels because of the slightly different CGs.

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Come on Guys, it can't be that hard getting under 200lbs... 

 

Borile evidently did it with a Chinese 230cc electric start engine!  Which would be the equivalent to the CRF230 Honda.  Of course his was using more street oriented suspension, but the CR85/CRF150r forks would be as light as the 40mm units that he used.  Same for the disk brakes off the small Hondas... 

 

http://www.twowheelsblog.com/post/10485/borile-multiuso-a-unique-multi-purpose-bike-from-Italy

 

Check out the offroad model with aluminum uni-body tank/frame in the photos.  Looks like maybe a bigger 250cc engine in that one.

 

Swiss

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For those last 2-3lbs. of weight loss for your bike plans! 

 

http://www.de-tris.com/

 

Swiss

 

Yes they are lighter than the CRF and KTM mini-bike conversion wheels...  Only about $2000 for the set if I understand their pricing!!

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I'm near the end of a kitchen renovation so now I can devote some time to bike projects. 

 

In a previous post I discussed some component weights but I think the break thru in weight reduction will be to use  light weight wheels from a Trials bike (I posted some weights from my Montesa 315R), and a lighter frame. I've observed over the years that frame weights seem to be 25 +/- lbs except for Trials bikes. My Montesa has an aluminum twin spar frame of Honda design that weighs 16 lbs, so there are opportunities.   

 

My 315R front wheel (w/ tire) is 6lbs lighter than a XR200 front wheel.

The rear wheel (w/ tire) is 4lbs lighter.

The 315R frame is 10lbs lighter.

 

So there is 20lbs.

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My 315R front wheel (w/ tire) is 6lbs lighter than a XR200 front wheel.

The rear wheel (w/ tire) is 4lbs lighter.

The 315R frame is 10lbs lighter.

 

So there is 20lbs.

 

To add to what Chuck has stated above

 

Weight removed from rotating and sprung components

contributes more to improving real and perceived performance

(acceleration, braking, handling & ride) than weight removed

from static components.

 

Subtracting 10 lbs from the outer periphery of the 21"/18" wheels

of a 23 HP bike like an '84 XR200 will have the effect of adding

substantial HP.  Search on terms like Moment of Inertia and

Effects of Rotational Inertia.

 

Now that I've composed this post, I reflect on the fact that the

thread is ten pages at this point.  So the aspect of inertia has

certainly already been discussed.  if so, well, my bad ...

Edit - a Zombie thread, back from the dead on top of my

probable redundancy.

 

Edit II - Change HP claim from 30 to 23

Edited by EddyCurr

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30hp?

 

Special edition, only released in Alberta.  Never understood why

everyone is so down on the twin-carb 4 valve RFVC until I realized

that the rest of you got the 23 HP version.

 

In a more serious vein, thank you for pointing out the error.

 

As for the original point - removing 10 lbs from the wheels will have

a more noticeable effect than 10 lbs from the static structure.  If the

budget doesn't permit taking it all off, cut the rotating/unsprung wgt

first.

Edited by EddyCurr

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Never understood why everyone is so down on the twin-carb 4 valve RFVC until I realized that the rest of you got the 23 HP version.

The twin carb RFVC 84 & 85 motors are ~ 17 lbs heavier than their 2 valve counterparts with a minimal amount of gain.

 

It is basically an 84/85 XR250R motor that has been destroked.

 

We have one poster on here who had Al Baker do him up a 265 for his 84 XR200R, which makes total sense, as you would need the additional cc to compensate for the additional weight. 

 

My educated guess they just took the connecting rod and or a full crank from an XR250 and put it in his and bored it out a bit to hit the 265cc. 

 

Back in my younger days had an 85 XR600R with the twin carbs, nothing but good things to say about performance, other than carb(s) tuning could be a bit tough to dial in. 

 

I am guessing and I mean am guessing that the 2 valve motors have about 13 hp and the 4 valve motors closer to 14 to 16 hp. 

 

Michael 

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The twin carb RFVC 84 & 85 motors are ~ 17 lbs heavier than their 2 valve counterparts with a minimal amount of gain.

 

It is basically an 84/85 XR250R motor that has been destroked.

 

We have one poster on here who had Al Baker do him up a 265 for his 84 XR200R, which makes total sense, as you would need the additional cc to compensate for the additional weight. 

 

My educated guess they just took the connecting rod and or a full crank from an XR250 and put it in his and bored it out a bit to hit the 265cc. 

 

Back in my younger days had an 85 XR600R with the twin carbs, nothing but good things to say about performance, other than carb(s) tuning could be a bit tough to dial in. 

 

I am guessing and I mean am guessing that the 2 valve motors have about 13 hp and the 4 valve motors closer to 14 to 16 hp. 

 

Michael 

Yes the 84-85 XR200R motor was a de stroked motor compared to the previous XR200 but it was more than that.

 

I owned a 84 XR250R and friends owned some RFVC XR200Rs and my memory says the RFVC XR200R was a small bore XR250R plus all of the other changes needed for the smaller engine size. Here is some data that may explain how some have mix/matched RFVC components to acheive different displacements.

 

Model.......................... Bore........ Stroke......... Displ

XR200 80-02 2 valve... 65.5.......... 57.8........... 195

XR200R  RFVC........... 67............. 56.5........... 199

XR250 84-85 /XL........  75............. 56.5........... 250

XR250 86-04............... 73............. 59.5........... 249

 

The 84-85 250 cylinder and piston provides a bolt on big bore for the 86-95 engine. And the 200 is easily converted to a 250 with the same cylinder, or a 280 with the 75mm cylinder and later 59.5mm crank.

 

I've ridden RFVC 200s and I don't think they have more than 1-2 HP over a 2 valve motor, but they weigh 17-20 lbs more.   They do however have a flatter or broader power band than the 2 valve motors, I was able to better climb mining slag piles with the RFVC 200s, but still preferred the 2 valve motor for trail riding. The counter balance shaft made them a smoother motor than the 2 valve motor.

 

Since the frames were the same for the 84-85 XR200R/XR250R I'd quickly convert a 200 to a 250 with a big bore cylinder. With all due respect for my friend; just saying that if I had the weight I'd want the displacement. 

Edited by Chuck.

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Ok, here is another little bit of weight off the 200. Xr600 swing arm axle.ImageUploadedByThumper Talk1400460544.486383.jpg

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Brought home weight scale from work;

 

1) 86 XR250R Swing Arm - 8lb 1oz (Removal of Chain Guide & chain slider)

2) 90 XR200R Swing Arm - 10lb 5 oz (Removal of Chain Guide & chain slider)

3) 86 XR250R Brake Hub - 1lb 7 oz (Aluminum brake arm) (Magnesium Hub)

4) 90 XR200R Brake Hub - 1lb 14 oz (Steel brake arm) (Aluminum Hub)

5) 87 XR200R Brake Hub - 1lb 12 oz (Aluminum brake arm) (Aluminum Hub)

 

So dropping ~ 3 lbs at this point, not a lot, but it's a start.

 

Next is the swap of the aluminum rear sprocket for the steel.

 

I will be hard anodizing the rear sprocket this week, it won't look as aesthetically

pleasing compared to the non anodized sprocket, but I am guessing it will be a

conversation piece that will get a lot of trial riders attention when stopped. I am

hoping the hard anodize will help with the longevity of the rear sprocket.  

 

At least it will be a close match to the engine color. 

 

Michael 

Edited by KTM520EXC

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ImageUploadedByThumper Talk1409090283.721514.jpg

This is with half a tank of gas in my '82 200r, I think I can get it under 200 dry if I keep whittling away at it. I've done most of the "easy" stuff. I wonder if PBI can cut me a 428 rear sprocket?

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